Modal Popup and WebPages ?

Is there any way to show different webpages inside modal popup or there is some different way ? From different webpages I mean, based on user selection .....

You can use the Dynamic* propertied of the modalpopup to load the content dynamically via a web service. The DynamicContextKey allows you to provide context to the web method that allows you to load different content depending on the value passed in.

You could also programmatically control the display of the modalpopup by using a hidden button as the TargetControlID and calling Show() manually. This allows you to postback and load the content according to the user selection.

Can you please provide an example which I can follow ?

The easiest way I can think of, is using an iframe inside the modal popup and setting it's src before showing popup.

Modal PopUp Extender

Based on the video example about using modal Popupextender. But the only changes i did is replace the option controls to textbox controls. The flow will only display the text on what I've inputted on the textbox in the modal window. The problem is how am I going to refresh the value of the textbox to null everytime I clicked the button to popup the modalwindow?

This might help:http://forums.asp.net/t/1137922.aspx